This application is related to a copending application entitled "Contact Insect Repellents" and filed concurrently herewith.
This invention relates to new and useful compositions of matter suitable as volatile insect repellents. More particularly, this invention relates to the use of maleic anhydride/alpha olefin polymers to increase the residual activity of volatile insect repellents.
Insect repellents have historically been selected on the basis of their persistence on the skin. Unfortunately, the usual topically applied insect repellents, such as diethyl toluamide, are fairly volatile, and therefore, have the disadvantage of giving protection only for relatively short periods of time due to their rapid evaporation and/or absorption by the skin. Both problems, absorption and evaporation, necessitate frequent applications which are bothersome and time consuming.
Adding adjuvant materials to increase the persistence of insect repellents was reported as early as 1928 for a formula consisting of oil of citronella, spirits of camphor, oil of tar, oil of pennyroyal and castor oil. Mehr et al., Laboratory Evaluation of Controlled-Release Insect Repellent Formulations, J. Am. Mosq. Control Assoc., Vol. 1(2):143 (June, 1985). The Mehr et al. researchers tested the persistence of several controlled-release formulations of diethyl toluamide, or more specifically, N,N-diethyl-3-methylbenzamide. Diethyl toluamide is commonly known as deet. These formulations consisted of microcapsule and free-repellent formulations containing hydrophilic vinyl polymers, such as polyvinylpyrrolidone.
U.S. Pat. No. 2,808,359 discloses that absorption by the skin and evaporation are reduced by mixing insect repellents with hydroxyalkyl esters of dicarboxylic acids, including bis(2-ethyl-3-hydroxy-hexyl) maleate. Other patents also disclose the use of various materials to extend the residual activity of insect repellents or slow release pesticides. See, for example, U.S. Pat. Nos. 2,884,355, 4,435,383 and 4,489,056.
U.S. Pat. No. 4,358,573 teaches that maleic anhydride/alpha olefin terpolymers are useful as mold release agents, slip agents and additives to floor polishes. They are not said to increase the residual activity of volatile insect repellents.
Accordingly, a long-standing need exists to provide an insect repellent composition for topical and/or surface application with improved residual activity, i.e., the period of repellent activity after application.
Deet, as well as other insect repellents, exhibit a greasy "feel" when applied to the skin. Accordingly, a need exists to improve the tactile "feel" of deet and other repellents in topically applied compositions.